In a lens unit, a structure may be adopted in which at least one of a plurality of lenses is press-fitted and fixed to an inner side of a lens barrel. Further, when a lens unit is used in an imaging device, a structure may be adopted in which a female screw formed on an inner peripheral face of a holder is engaged with a thread groove which is formed on an outer peripheral face of a lens barrel so that the lens barrel and the holder are integrated with each other and thereby an imaging element is held through the holder (see Patent Literature 1).